Bishop Exchange

Bishop Exchange
☖ pieces in hand: 角
987654321 
香桂 金王  桂香1
 飛銀   金  2
歩 歩歩歩歩銀歩歩3
      歩  4
 歩       5
  歩    歩 6
歩歩銀歩歩歩歩 歩7
  金   銀飛 8
香桂  玉金 桂香9
☗ pieces in hand: 角

In shogi, Bishop Exchange (角換わり or 角換り kakugawari) is a Double Static Rook opening in which each player's bishop is captured relatively early so that they keep their bishops in hand.

In contrast to Double Wing Attack and Side Pawn Capture openings, but like the Double Yagura opening, the Bishop Exchange opening aims to prevent each player from trading off each other's rook pawn. Both players move their left silver to the 77 and 33 squares (Black and White, respectively) in order to accomplish this goal in both Bishop Exchange and Yagura openings.

White's bishop trade with ☖85-Pawn

1. P-76. Black chooses the flexible option of activating their bishop.

1...P-24. White pushes their rook pawn showing their intent to play Static Rook.

Note that if White had opened their bishop diagonal (1...P-34) instead of 1...P-24, then a regular Bishop Exchange opening would no longer be possible since Bishop Exchange openings have Black's bishop positioned on 77 followed by their left silver positioned on the same 77.[lower-alpha 1] If White's bishop diagonal is open before the Black's bishop has moved to 77, then Black will not be able to position their silver on 77 in recapturing White's bishop.

2. P-26. Black mirrors White in activating their rook with a rook pawn push. Thus, the game can now be seen as a Double Static Rook game.

Bishop Exchange
up to move 4
☖ pieces in hand: –
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香桂銀金王金銀桂香1
 飛     角 2
歩 歩歩歩歩歩歩歩3
        4
 歩       5
  歩    歩 6
歩歩 歩歩歩歩 歩7
 角     飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –

2...P-85. After the third move by Black, White has a choice between advancing their rook pawn further (2...P-85) or defending the head of their bishop with a gold (2...G-32) from Black's possible second file pawn attack.

The rook pawn option (shown here) is more suggestive of a Bishop Exchange opening since White is threatening to exchange eighth file pawns before Black exchanges pawns on the second file which, if allowed by Black, may lead to White gaining the initiative.

While Black could advance their rook pawn on the second file as well in response to White's 2...P-85, doing so is more suggestive of a Side Pawn Capture opening in professional play since modern Bishop Exchange openings generally delay a second file pawn push for later in the game. Therefore, Black's most common response to White's rook pawn push is to move their bishop to the seventh file preventing White's pawn exchange, which usually leads to a Bishop Exchange opening.

White's other option for their second move is 2...G-32. This move is somewhat more flexible than 2...P-85 as the opening at that point would still be ambiguous between a Bishop Exchange opening (1. P-76 P-84, 2. P-26 G-32, 3. G-78 P-25, 4. B-77 P-34, 5. S-88) and Side Pawn Capture opening (1. P-76 P-84, 2. P-26 G-32, 3. G-78 P-34 4. P-25 P-85 5. P-24).

Classic vs modern

After White's rook pawn (2...P-85), Black now has two options. The older option found in Classic Bishop Exchange games was to advance Black's rook pawn (3. P-25) since White's bishop head is unprotected. (See § Classic Bishop Exchange below.)

However, this move has been replaced in more recent Bishop Exchange games (see § Modern Bishop Exchange (Delayed rook pawn push) below) where the P-25 option is delayed. Instead, Black protects the eighth file with their bishop (3. B-77).

Nonetheless, although disfavored and currently not as popular, a some professional players have played these positions 2015–2018.[1]

Modern delayed rook pawn

Bishop Exchange
up to move 5
☖ pieces in hand: –
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香桂銀金王金銀桂香1
 飛     角 2
歩 歩歩歩歩歩歩歩3
         4
 歩       5
  歩    歩 6
歩歩角歩歩歩歩 歩7
      飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –

3. B-77. In modern Bishop Exchange openings, Black moves their bishop to the 77 square in order to prevent White from exchanging pawns on the eighth file instead of P-25. This delay of advancing their rook pawn is known as 飛車先保留 (hisha saki ryūgata) in Japanese.[lower-alpha 2]

Delaying the rook pawn push is more flexible in that is does allow Black to position their right knight on the 25 square later in the opening, which is not possible if the rook pawn positioned on that square. Thus, a P-25 pawn narrows the opening possibilities for Black.

3...P-34. White opens their bishop diagonal attacking Black's bishop on 77, which is a vulnerable position since Black's bishop diagonal is also open.

4. S-88. Black moves their left silver to defend the bishop. If the bishop is captured, then the silver can move to 77 and still keep White from exchanging pawns on the eighth file. This is the quintessential position of the Bishop Exchange opening.

Black's bishop positioned on 77 is only defended by their left knight (before moving the silver). If White were to capture the bishop now (4...Bx77+), then Black's knight would be forced to capture (5. Nx77). This would leave the eighth file unprotected from White's rook pawn attack. Therefore, defending the bishop with the silver is important for defense.

Classic Bishop Exchange

Classic Bishop Exchange
up to move 5
☖ pieces in hand: –
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香桂銀金王金銀桂香1
 飛     角 2
歩 歩歩歩歩歩歩歩3
         4
 歩     歩 5
  歩     6
歩歩 歩歩歩歩 歩7
 角     飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –

3. P-25. In Classic Bishop Exchange openings, the natural move after White's P-85 was to likewise advance Black's rook pawn. Since White must defend their bishop head from this threat, Black need not immediately protect their eighth file with B-77 and could instead make 3. P-25. However, the rook pawn push at this early juncture is now becoming disfavored by professional shogi players.

Classic Bishop Exchange
up to move 5
☖ pieces in hand: –
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香桂銀金王銀桂香1
 飛    金角 2
歩 歩歩歩歩歩歩歩3
         4
 歩     歩 5
  歩      6
歩歩 歩歩歩歩 歩7
 角     飛 8
香桂銀金玉金銀桂香9
☗ pieces in hand: –

3...G-32. Since White's bishop diagonal is closed, White must protect their bishop head (the 23 square) from Black's second file pawn attack by moving their gold to the third file.

If White failed to protect 23, then after a pawn exchange, Black can drop their pawn on 23 capturing White's bishop in a later move. (Cf. the similar case: Double Wing Attack § Blunder: White's failure to defend bishop.)

Variations

After the initial opening, the Bishop Exchange opening has several possible variations that follow:

Each of these use a different right silver strategy

There are also other variations that use different opening move sequences:

  • Tempo Loss
  • Wrong Diagonal

Other variations:

  • Tomioka Bishop Exchange (富岡流 tomioka-ryuu)

Black's early ☗45-Knight jump

Early N-45
☖ pieces in hand: 角
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香桂   王 桂香1
 飛  金 金  2
歩 歩銀歩歩銀歩 3
   歩  歩 歩4
 歩   桂 歩 5
  歩  歩歩 歩6
歩歩銀歩歩    7
  金玉  銀飛 8
香桂   金  香9
☗ pieces in hand: 角
14. N-45
Early N-45
☖ pieces in hand: 角 歩
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香桂   王 桂香1
 飛  金 金銀 2
歩 歩銀歩歩   3
   歩  歩飛歩4
 歩   桂   5
  歩  歩歩 歩6
歩歩銀歩歩    7
  金玉  銀  8
香桂   金  香9
☗ pieces in hand: 角 歩
14... S22

15. P24 Px24

16. Rx24

An early knight attack by Black before developing the usual Reclining, Rushing, or Climbing Silver offense.

The attack aims to (i) attack White's silver on 33 forcing it to retreat to 22 allowing Black to trade off the rook pawn on the second file and (ii) subsequently attack White's undefended rook with a B*71 bishop drop which simultaneously defends the 53 square which is already under attack by Black's knight on 45.

An important point of Black's attack depends on 53 square being defended by White's single gold on 52. If White moves their right silver to 62 and keeps it there instead of moving it 72, it defends 53 as well as preventing the 71 bishop drop by White.

Black's bishop trade with ☖22-Bishop ☖32-Gold ☖42-Silver

A less common variation has White move their left silver from the 31 square (where was defending the bishop on 22) to the 42 square instead of making a bishop trade themselves. This positioning leaves the bishop only defended by the gold on 32.

If Black does not respond to this configuration now, White can reject a Bishop Exchange opening with their next move by moving the silver up to 33 where it forms the initial construction of a Yagura castle leading to White's likely Yagura opening where an early bishop trade is no longer possible. Since Black's structure is basically a Bishop Exchange form, transposing to a Yagura position can be awkward. Thus, Black usually initiates the bishop trade at this point. Although this trade losses tempo, White usually must move their gold from 22 back to 32 for proper defense and must, therefore, loss a tempo with this move as well resulting in no overall gain in tempo for White.

Black's bishop trade with ☗25-Pawn

Although Bishop Exchange openings are typically characterized by White advancing their rook pawn to the middle rank with P-85, which is the move that triggers Black's B-77 defense in the first place, there is a sort of reverse Bishop Exchange opening where Black advances their rook pawn up the second file to the 25 square, which similarly triggers White's to move their bishop to 33. In this case, it is Black (instead of White) that initiates the bishop trade.

Comparison of different Bishop Exchange positions

Before the bishop trade off

The bishop trade

After the bishop trade

Two moves after the bishop trade

See also

Notes

  1. ↑ Note that this comment about a Bishop Exchange opening being prevented by having both players's bishop diagonals open (with 1. P-76 P-34) is true for the regular Bishop Exchange opening, which requires White's bishop diagonal to remain closed initially (by White not pushing their third file pawn). The Japanese term 角換わり kakugawari without modification refers to this class of openings. However, the 1. P-76 P-34 sequence still allows for a possibility of a Tempo Loss Bishop Exchange opening. However, this formally distinct opening is not referred to simply with 角換わり kakugawari. Although there are similarities between Bishop Exchange openings and Tempo Loss Bishop Exchange openings, the Tempo Loss Bishop Exchange is treated separately in its respective article.
  2. ↑ Note: this delay is also found in modern Double Yagura games as well even to the point of not moving the rook pawn up to 26 early (under the term 飛車先不突き矢倉 hisha saki futsuki yagura).

Bibliography

  • Fairbairn, John (1986). Shogi for beginners (2nd ed.). Ishi Press. ISBN 978-4-8718-720-10.
  • Hosking, Tony (1996). The art of shogi. The Shogi Foundation. ISBN 978-0-95310-890-9.
  • Kitao, Madoka (2011). Joseki at a glance. Translated by Kawasaki, Tomohide. Nekomado. ISBN 978-4-9052-2501-0.

References

  1. ↑ http://kyokumen.jp/positions/126994
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